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=============================================================================
FreeBSD-EN-20:12.iflib                                          Errata Notice
                                                          The FreeBSD Project

Topic:          iflib watchdog timeout resetting idle queues

Category:       core
Module:         kernel
Announced:      2020-06-09
Affects:        FreeBSD 12.1
Corrected:      2020-01-10 18:29:05 UTC (stable/12, 12.1-STABLE)
                2020-06-09 16:11:54 UTC (releng/12.1, 12.1-RELEASE-p6)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

iflib is a framework that contains common code for network drivers to use,
reducing code duplication. One function it contains is a "watchdog" that
periodically checks the driver's software Tx queues to see if they're hung.

II.  Problem Description

The iflib watchdog would sometimes trigger a false positive queue hang just
after a link state change.

III. Impact

The iflib framework would print messages for the affected devices such as

"igb0: TX(2) desc avail = 1024, pidx = 0"

and would stop allowing Tx traffic to be sent.

IV.  Workaround

No workaround is available.  Systems that do not use iflib-based interfaces
are not vulnerable.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date, and reboot.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for errata update"

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-20:12/iflib.patch
# fetch https://security.FreeBSD.org/patches/EN-20:12/iflib.patch.asc
# gpg --verify iflib.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r356605
releng/12.1/                                                      r361971
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=239240>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-20:12.iflib.asc>
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